Automatic sorting machines cause objects or articles to travel along a path wherein the objects are scanned by known types of optical-electronic sensors which determine whether an object is acceptable or should be rejected. Downstream of the scanning location there are means actuated by the sensor to eject or divert an unacceptable object from its normal path of travel to a collection station for acceptable objects to a path which leads to a collection station for rejected objects, i.e., rejects. Many types of such rejection means or systems are known. Among these are those which use an air jet to reject or divert an unacceptable object from its normal path of travel. Exemplary of such air rejection systems are the disclosures of U.S. Pat. Nos. 2,967,614 and 4,035,636. While air rejection systems are practical and useful for machines for sorting small objects, e.g., raisins, nuts, rice grains, etc., they are impractical for sorting large objects such as tomatoes, oranges and other objects which may be intermingled with stones, dirt clods, etc. Jets of air of sufficient size and velocity to move such large objects create moisture and stir up dust which have a detrimental effect on the optical elements of the scanning sensors. Moreover, such air jets require large amounts of power so that they are particularly unsuitable for mobile sorting machines.
Mechanical rejection systems also are known. While they are fairly energy efficient, in general they have several disadvantages among which are short life, slow operation, and inflicting damage to the rejects. Mechanical rejection systems presently in use may be classified into three different types, "kicker", "bopper", and "deflector". A fourth type, the "trap door", is known but is not in general use because it is so slow, clumsy and expensive as to be impractical for commercial application.
The kicker type of mechanical rejection system is similar in a sense to a baseball bat. The "bat" or paddle is hinged at one end and operated by an air cylinder or an electric solenoid to knock an object out of its normal path of travel into a path which leads to a collecting station for rejects. Kicker systems have been used effectively for sorting objects such as tomatoes or onions from dirt clods. Dusty operating conditions, arising from dirt clods, however, tend to wear out the seals of air cylinders. Moreover, since scanning sensors are not perfect, sorters sometimes reject acceptable objects. For this reason, rejects frequently are run back through the sorting machine. Kicker rejection mechanisms have the disadvantage that they tend to damage anything they reject. For example, they will severely damage an otherwise acceptable tomato. Thus, kicker systems do not lend themselves to a rerun of rejects.
The bopper type of mechanical rejection mechanism is, in a sense, like a boxing glove mounted on the end of a piston rod of an air cylinder. This mechanism is simpler than that of the kicker type, but its life is shorter because the piston of the air cylinder must have a longer travel than that of the kicker mechanism because the latter takes advantage of a lever action to limit the extent of piston travel. Moreover, the bopper mechanism has almost the same reject-damaging defect as the kicker mechanism.
The deflector type of rejection mechanism is used wherein the normal path of travel of the articles or objects being sorted has a section involving a free-falling trajectory as disclosed, for example, in U.S. Pat. Nos. 4,095,696 and 4,155,456. When an object is to be rejected, a long paddle is projected into the free-fall section of the normal path to divert or deflect a rejected article to a different trajectory which leads to a station for collecting rejects. In this type of system very little, if any, damage is done to a rejected article. Consequently, in this system, rejected articles can be rerun through the sorting machine. This system is speed deficient, however, as compared to the kicker and the bopper systems. Furthermore, it is somewhat more complex than the bopper system since the deflector mechanism uses both a paddle and an air cylinder or solenoid.
The present trend in automatic sorting machines is away from so-called "channelized" systems toward so-called "random feed" systems. In channelized systems, objects to be sorted are arranged in one or more parallel rows, each of which is scanned by a separate sensor. In the random feed system, objects to be sorted are simply deposited at random on a flat conveyor belt and scanned with a multiplicity of sensors. This system avoids the mechanical complication of arranging the objects in rows and so increases the through put for a given width of machine. It will be seen that the random feed system requires the use of many rejectors to insure that it is possible to reject an unacceptable object without disturbing its acceptable neighbor. This requires that the rejection system be small, simple, low cost, and reliable.